My 2002 Toyota Tacoma has some weird acceleration issues. It is 2WD, automatic, has around 134k miles. At first we thought it was due to altitude, but has resurfaced on normal streets as well. Additionally, it seemed to only happen during long drives and at high speeds, but today it occurred at around 40 mph when I floored it. Any suggestions would be greatly appreciated.
Please describe in detail your exact complaint with the acceleration. Is there a hesitation? Is there stumble? Just a lack of acceleration?
I would be looking at the fuel pressure under high output conditions. When were the spark plugs last replaced? Is the Check Engine Light ‘ON’ at this point? Have you pulled any Diagnostic Trouble Codes? Have you done any service to address this problem?
Also consider a plugged catalytic converter. Monitor the intake vacuum under high engine output at high RPM.
Hope to help.
Check engine light has not come on. No diagnostic trouble codes. While climbing a fairly steep hill, going 40mph or thereabouts, the acceleration faltered. Felt more like something was wrong with the gear; slippage or somesuch. Thought it might have been due to the altitude, but when we drove/coasted back to level ground, it was fine. It’s like a stumble I guess. Driving along fine, but I will feel a hesitation in the accelerator that starts very small, but will eventually cause lurching. I’m sorry if I’m not describing this well. Today, as I stated, I floored it to pass someone, and the stumble / loss of acceleration happened then.
Spark plugs were changed when this first happened, last July. No other service was done as the mechanics could not duplicate the problem.
Thank you for your reply. I will keep those issues in mind when I take it in again.
This is a known problem on toyota’s. It’s do to the ECM malfunctioning when the accelerator is pressed to the floor. Toyota will never acknowledge that this is a problem, but it is. I would just live with the it (the chance of increased and unstoppable acceleration or non at all) or just trade it in like I am going to do next month. Good luck 
If it has an automatic transmission one thing to consider would be torque converter clutch shudder. If you have an overdrive off (or O/D Off) button you could try driving around without the O/D for a while to see if its still a problem.
In addition to checking for exhaust blockage a load test of the fuel pressure would be good.